Method of forming sheet metal.



F. M. OPITZA METHOD OF FORMING SHEET METAL.

I APPLICATION FILED OCT. 1', I918, 7 1,316,636. PatentedSvpt. 23, 1919.

1Q) 21 W1 22 1Q 22) 225 25 I m 5 2 9.16 QZ'QUenZ w flf, $40.16; k

' a pleasing appearance of the radiator.

niurrnn s rarjas earner ora ion.

FEED M. O'PITZ, 0F RACINE, WISCONSIN, A$IGNOB TO PERFEX RADIATOR COMPANY, 01? RACHE, WISCQNSIN, A CORPORATION OF WISCONSIN.

METHOD 0F FORMING SHEET METAL .epplicetionfiled October 31, 1918.

my first papers, residing at Racine, in the county of Racine and Stateof Wisconsin, have invented aicertain new and usefullmprovement inMethods of Forming Sheet Metal, of which the following is a full, clear,

concise, and exact description, reference being had to the accompanyingdrawings, forming a part of this specification.

My invention relates to a method of forming sheet metal.

While the invention is particularly-useful in connection with theformation of radiator tubes. 1 do not intend to limit the invention tosuch use or purpose only.

adiator tubes made up of single pieces pen'ding case, Serial No.200.252, filed March 5. 1917, of which the present application is animprovement.

For the sake of efficient operation, it is desirable to make the tubeswith as large a superficial radiation area as possible and to bring allparts of the Water or the cooling medium near the radiating surfaces tocool the contents of the tubes. It is also desir able that the Walls ofthe tubes through which transfer of heat is to be accomplished should beas thin as mechanical strength will permit. To be able to make the tubeout of sheet metal is desirable, because of the cheapness of such sheetmetal and because of. the strength of the tubes when thus formed. Thereis also a strong: demand for To meet these requirements 1 form the tubesoutof sheet metal with lateral corrugations ofsuch form as to provide.when these tubes are assembled into a core, a umber of round cylindricalpassages for the air between the corrugations of adiacent tubes The par:tlifllltll formation which I employ gives the appearance of a solidblock with a large number of closel grouped cylindr cal air passagesthrough the core with a of vertical fins or flanges between rowe of ourSpecification of Letters Patent.

Patented se t. as, rare.

Serial No. 25?,764.

cular holes where the fold or seam along the front face of each tube. ismade. The holes of one vertical row are offset by one-half the pitchdistance with respect to the holes of adjacent rows so that a maximumnum-,

ber of holes is possible.

This arrangement requires the ofl'settmg of the corrugations of the tubeand such offsetting has heretofore been a practical diliiculty becauseof the uneven drawing of the metal, as heretofore practised.

To form the circular holes it is necessary that the tubes have lateralcorrugations forming complete halves of the sides of the holes, Thetubes are made of a thickness substantially equal to the diameter of theholes and semi-circular depressions lie on each side of the centralflange or seam. The front and rear faces of the tubes are made to lie asnearly as possible in planes parallel to the front and rear faces of thecore in the preferred form of my invention, although this is notessential; The corrugations are, in the preferred form of my invention,at rig'ht'angles to the face of the core, but this also may be varied.

I am aware that heretofore tubes have been made with corrugations alongthe sides and that said tubes have been made of a single sheet of metal,but no one heretofore has produced a tube havingcomplete semicirculardepressions to form complete circular holes so that the air within thehole is in contact with the coolingmedium on all sides.

Furthermore the production of a semi-circular depression with asubstantially square integral end flange is novel and has not herenovelprinciple of working the sheet metal,

i and it is with the application of this novel principle of workingsheet metal that the present application is concerned.

I have found that where it is desired to produce a corrugated metal tubeor part of a tube in which the side Walls are to be corrugated and theend walls are to be plain,

- that the metal along the margins which form the end walls may beshrunk sufliciently to supply the extra material or metal required toform the corrugations. I

This is opposed to the teachings of the maintained at their originalthickness and the parts to he corrugated are stretched in order tosupply the surplus required for the corrugations.

The general principle involved is that where a plain sheet of metal isto be distorted out'of a plane shrinking of one part of the metal orsheet may be accomplished 10. under certain conditions with bettereifcct and more easily than stretching or expand ing the other part. Thedecision between shrinking and stretching should be made upon the basisof the amount of metal that must be moved by one as against the other,and by any special diiiiculties which would be involved. .l-inothersubsidiary principle that is involved relates --to the matter of formingthe metal about-a sharp shoulder or projection. Where the shoulder orprojec tion is of such a character or shape that the metal would bestretched along a sharp" line or point, I find that it is possible toshrink or fold the metal about the form or projection so as to leave thedesired shape with out damage to the metal in any way.

In order to explain to those skilled in the art the manner in whichthese principles are to be applied in actual working of sheet metal, andto explain a specific embodiment of the invention, I shall now describein connection with the accompanying drawings the manufacture of radiatortubes for forming the core of a radiator.

In the accompanying drawings- Figure 1- is an isometric view of apart ofthe core of a radiator employing tubes constructed in accordance with myinvention;

Fig. 2 is a fragmentary front elevation of a Radiator core of the formshown in Fig. 1;

1g. 3 isometric projection of the sheet of metal formed according to thefirst step of my in-. vention'; Fig. 4: is a similar diagrammatic viewin isometric projection showing the step of corrugating' the bottom andedge wall of each of the gutters or grooves shown in Fig. 3;

illustrating diagrammatically the manner in which the metal is shrunkalong the fla g that is the marginalportion, and the end walls to formthe semi-circular corrugation;

' 56 Fig. 6 is a front elevation of a part of the finished corrugationshowing the manner in which the" metal has been folded along the endwalls of the tube or part of the tube;

Fig. 7 is a fragmentary sectional view taken from the inside withrespect to Fig. 6 showing the manner in which the'metal is folgedinwardly along the end-walls of the t1! Fig. 8 is a sectional view takenon the I5 line 8--8 of ig. 6 showing the folding and is a diagrammaticillustration in' Fig. 5 is a fragmentary isometric view thickening ofthe metal "alone; the margin and end walls of. the tube;

Figs. B'tq 21 inclusive illustrate various steps in the manufacture ofcommercial radiator tubes. 7

Fig. 9 is a plan view of a sheet passing through the first stage offolding toform the margins and end walls of the tube; r

Fig. 10 is an end view of the same;

igs. 11 and 12 are a planview and an 5 end view respectively of thesecond step which consists in forming the corrugation in the sides ofthe tube and shrinking the ends and margin;

Figs. 13 and 14 are-plan view andend View respectively of the sheetafter it has been moved forward one pitch distance in.

the dies.

liigs: 15 and 15 are planview and end view respectively of the sheetafter it has advanced completely through the dies. show ing the creasingalong the central margin for folding;

Fig. 17 is a plan view ofthe corrugated and creased sheet after it hasbeen trinuned he in preparation for folding;

. Fig. 18 is an end view of the same taken from the left of Fig. 17;

Fig. 19 illustrates the step of folding the. central margin and-startingthe foldofithc edge margin, which step is accomplished by a power press;

Fig. 20 is an end view of the tube after; the fold has been rrimpletedand the seam j has1 been closed at the one edge of the tuhet' led an iFig. Zlis a side view of the completed tube taken from the left of Fig.20.-

' The radiator which I preferably form is of the vertical tube typehaving suitable we headers at the upper and lower ends oi the tubes,these tubes being grouped together in contact to form a solid core, asection of which is illustrated in Fig. l. The 1 I core 1 comprises theseries oi. tubes 2 which lit-1 have water passageways 3 passingvertically-g through the same. .The si walls of they tubes 2 areprovided with the semi-circular depressions or corrugations i-{betiireenwhich,

remain the flat side walls 5 which are placed 3.3. in contact withadjacentsimilar walls 'off the tubes on each side of-the articular tube.These semi-circular deprcssiilns, when thus brought into register, formthevcylindricai V.

'holes or air passagew'ays 6 mm liwhich we the air for cooling theliquid within the core 1 passes, with the flanges or some? and 8, whichare formed respectively it folding the sheet and by joiningthememargins, as will be described later.

To form the tubes I provide WStflp of sheet metal of suitable width andthickness such as disclosed inmy copending applies its mimosa tionSerial No. 257,765, filed Uotober 11,

1918. The tube might be made up of two sheets of metal one for each sidebut preferably 1 form both sides simultaneously and form the tube byfolding along a center margin, as will bedescribed later.

The. sheet fed into suitable dies which form the sheet into the doublegutter shown at the right of Fig.9 and shown in Fig. The two gutters 11and 12 are formed with the side margins 13 and 14, respectively, and thecentral margin 15 which forms the folding margin to form the completetube. While I have shown in Fig. 3 complete gutter formed in thismanner, it will be understood that the step of corrugating the gutter asfast as it is formed is found in practice to be preferable, as theseoperations may be performed by a single pass through a suitable stampinor punch press, as isdescribed in my copencing application. The gutter11 has the bottom Wall 16 which becomes the side ,Wttll of the tube whencompleted, and the end Walls 1? and 18 which become the front and rearend faces of the tube when completed.

The gutter 12 is similiarly formed with the bottom wall 19 and the endwalls 20-and 21. A description of the operationof forming one gutterwill suffice for both. The depth of the gutters 11 and 12 issubstantially half of the thickness of the finished tube.

So far in forming the tube, the metal has not been disturbed, either bystretching or,

thereafter flattens out the margins and eX- tends the formation of thegutter. Reference is made to said application for a disclosure of acommercial form of corrugating die press. The corrugations 22 in thegutter 11 are offset with respect to the corrugations in the gutter 12by one-half the pitch distance so that the circular holes 6 formedbetween tubes are staggered by the same amount. The first step in thecorrugating dies forms a complete corrugation at 22 in the gutter 11 andbelief a corrugation 1n the gutter 12, as s'hown inFigs. 1'1' and 12.

I Thereafter thesheet is advance d by a strip equal to the pitchdistance between corrugations, the second step being illustrated inFigs. and. 14:.

The die which forms the gutters thousandths of an inch.

As these corrugations 22 are formed, the metal along the margins 13, 14and 15,'and along'the end walls l7, 18, 20 and 21 is thickened byshrinking, this being indicated by the shading 23 and the increasedthickness indicated in Figs. 12, 1% and 16. The

. thickness at the points indicated by the referthe central margin 15 isgiven a slight crease,

as indicated at 24:, by a suitable groove and projection upon thecoiiperating part of the dies. Durin the corrugating operation thethickening o the metal along the margins and end Walls results informing on the surfaces of these parts a great number of small surfaceWrinkles which are indicated by the shading 23. The forming of the line24 which is in the nature of a very slight crease is to insure thatallpf the surface Wrinkles have been flattened out along the line wherethe folds is to'be formed. 24 which I term a crease need be formed onlyto the extent of insuring that there are no transverse wrinkles runningacross the central part, which creases, if theydid exist, would tend toform a ragged or uneven-fold. lhe flattening out of the surface Wrinklescaused by shrinkage of the sheet does not produce an absolutely flatsurface, as the Wrinkles are still visible, but for practical purposesthese surface irregularities are immaterial.

After the sheet has been completely corrugatedit is cut into suitablelengths, and the margins 13 and 14: which are to form the scam are thentrimmed by runnin the sheet through a suitable shears Whic is guidedalong the central groove 25 formed between the Walls '18 and 20 It willbe noted that the margin 13 is of less Width than the margin 14. This isfor the pur pose of formin a folded seam. The corrugated sheet shown inFigs. 17 and 18is then placed in a suitable die and is folded along theline 24 on the central margin 15, as indicated in Fig. 19, and the edgeof the margin 13 is bent up as shown at 26 in Fig. 19. The tube in thecondition shown in Fig. 19 is then laid in a suitable die and is struckwith another die which closes the seam 8 by folding the metal of flange13 over the edge of the flange 14 into a folded seam, as

Hence this line shown in Fig. 20; A series of such tubes are thengrouped together into a core, the front and rear faces preferably, butnot necessarily, being dipped in solder to cause union between the adacent portions and to close the folded seam 27 where themargins 13 and14 have been joined.

I shall now endeavor, in connection with Figs. 3 to 18 inclusive, tomake clear the movement of the metal in forming the corrugated tubes.When the double gutter, as shown in Fig. 3, is formed, the metal isnovwhere warped as the margins 13, 1a and 15 lie in substantially thesame plane, and the end walls 17, 18, 20 and 21 lie in substantiallyparallel planes except for the small amount of taper necessary inpractice to give clearance to the dies. This taper has been somewhatexaggerated in the draw: ings. Considering the utter 11 shown in Fig. 3,independently o? the gutter 12, as

it is obvious that the formation of one is similar to the other, inorder to secure the corrugations 4 there must be greater lineal lengthof material in the bottom wall 16 than in the flanges 13 and 15 for thevery obvious reason that the circumference of the semicircle isconsiderably greater than the diameter of the semicircle. In order topro-' duoe this surplus of material either the metal in the bottom wall16 and in a part of the end walls 17 and 18, must be sufiicientlystretched to produce this surplus or 'the surplus of metal must besecured in some other manner. Independently of which way it is secured,I believe that I am the first to form an open trough or gutter and thencorrugate the bottom of the gutter with the corrugations running.through the end walls.

The particular manner in which I secure 4 the surplus metal for formingthe corrugations is by shrinking the metal along the margins 13 andvl5and, to a certain extent, the end walls 17 and 18. Consider the gutter11 after it has been corrugated, and it will be seen that the part ofit, as shown in exploded or dissected form-in Fig. 4, will consistofthickened margins 13' and 15 and thickened end walls 17 and 18' andthe corrugated side walls 16' of original thickness.

It is at once a parent, on comparing Figs. 3 and 4, that t e end walls17 and. 18 mnst take up a relatively large proportion of-the in themetal which it must undergo, it will be seen that the length as shown infull lines must be contracted to the length shown between dotted lines28 and 29, and the edge 30 of the bottom wall 16 must be drawn in to thedotted lines, must be displaced later.- ally in orderto permit thecorrugations to run through the end. wall. As the cylindrical die memberpushes the bottom wall upward and crushes the end walls 17 and 18, themetal within those portions of the end Walls is partly taken up bythickening of the metal between corrugation-s in the end walls and isalso partly taken up by crumpling or folding as is indicated in Fi s. 6,7 and 8. There is both an outward fol ing, as Shown at reference numeral33, and an inwardiclding as shown at reference numeral 34 in ,Figs. 6, 7and 8. This disposition of the metal can be clearly seen in the tubesafter they are formed.

As I have above explained, there is a tendency for surface wrinkles toform along the margins and along the end walls. This may be permitted toa greater or less extent, depending upon the closeness of the fit of thedie. s

I do not intend to be limited to the precise details shown and describedas my invention, as relating tothe formation of corrugated tubes and thelike, 1s broadly new.

I claim:

1. "In the method of forming a corrugated metal tube, the combination ofthe following steps :first forming a gutter having bottom walls and endwalls and marginal portions,

and then corrugating the bottom wall with corrugations which runthroughtheend wall. 2. The method of forming a corrugated metal tube havinguncorrugated portifis Y which comprises shrinking the uncorruga portionsto, provide a surplus of metal re? quired along the corrugated portions.

3. The method of forminga metal tube having corrugations along-part ofits walls which comprises shrinking the unmrrugated portion of the wallsandsimultaneously increasing the thiclmess thereof while maintainingtheportions of the walls to be corrugated at substantially the originalthickness. v q

' 4. The method of forming a metal tube having corrugations along partof its walls which comprises shrinking the uncorrugated portion ofthewalls and simultaneously increasing thethickness thereof whilemaintaining the portions of the walls to be corrugated at substantiallythe original thickness,

and oorrugating said latterfportion. .5. The method of forming a sheetmetal tube having corrugated side faces and in.-

corrugated end faces which comprises, the following steps: eor'rugatingthe side fag-res while mamtammg them atsubstanti'ally r. The method offorming a corrugated metal tube having uncorrugated portionswhichcomprises shrinking the uncorrugated portions and simultaneouslyincreasing the thickness thereof while maintaining the portions to becorrugated at substantially the original thickness, corrugating saidlatter portions and then forming a seam along the uncorrugated portions.

8. In a method of the class described, the

following steps; shrinking the marginal portion of a sheet of metal toproduce a fullness or surplus of metalat other portions, and corrugatingsaid other portions to take up fullness or surplus thereof. 9. Themethod of forming a tube of the lass described, whichconiprises thefollow: 'ng steps: forming a plain sheet into a gutcrhaving a flatbottom wall and flat side valls at. substantially right angles to theottom wall and flat marginal flanges lying substantially parallel to thebottom Wall, fore shortenin the entire gutter and simultaneously formingcorrugations in the 'bottom wall of the gutter, said corrugations extending into and through theside walls of the gutter.

10. In the method of forming a tube of the class described. thecombination of the following steps: forming a plain sheet into a. gutterhaving a. bottom wall and side walls, said walls being substantiall atright angles to the bottom .Wall, fore-s ortening the gutter to thickenthe side walls of the gutter and corrugating the bottom wall-o" thegutter while maintaining the metal said corrugations at substantiallythe original thickness.

11. The method of forming a tube of the class described, the combinationof the following steps: bending a plain sheet into the form of a gutterhaving bottom Walls and side walls, the side walls lying atsubstantially right angles to the general plane of the bottom wall ofthe gutter and pressing the bottom wallinwardly in a semicirculardepression, said pressure being extended through the side walls to crushthem edgewise to form a complete transverse semicircular corrugation.

12. The method of forming a sheet of metal into a tube which includesthe following steps, forming the sheet into sidewalls,

end walls and a joining margin, and forming cornug'ationsin the sidewalls extending through the end walls.

l3. Inthemethod of formin a sheet into a tube; the lcembination of tiefollowing steps: forming the sheet metal into a gutter having a bottomwall and side walls at substantially right angles to the bottom wall,then forcing a portion of the side wall inwardly to form a continuousgroove transverse to the gutter and simultaneously crushing the sidewalls edgewise to form a fold of the metal at each end of the groove.

'14. In the method of forming a sheet of metal into a tube, thecombination of the following steps: forming the sheet into a gut terhavin a bottom wall and side walls at substantidlly right angles to thebottom.

* wall, then pressing edgewise with a rounded forming tool upon the sidewalls and simultaneously. pressing the bottom wall in- I wardly to forma complete transverse groove across the gutter.

15. The method of forming tube iron:

sheet metal which comprises forming the sheet into a pair of gutterswith margins. at their outer edges and niiargins between them, thenforming a crease longitudinally centrally of said central margins, thentold ing the two gutters along said crease into the form of a tube, thenjoining the edges of said gutter to form a closed seam.

16. The method of forming a tube which comprises folding a sheet ofmetal rentinuously and progressively into a pair of gutters joined by anintegral margin, than oorrugating said gutters and simultaneouslyshrinking the metal along the central ma in, then. creasing the centralmar inand ending the two gutters toward each other and sea ing the freeedges of the same.

1'3. A radiator tube formed of sheet metal comprising unita j front andrear faces of greater thickness t ian the original sheet and corrugatedside walls of a thickness substantially equalto or very slightly lessthan that of the original sheet,

Mill

ill)

18. In a radiator, a tube havin front and.

rear faces and side walls, said si e walls being corrugated insubstantially semicircular rugations.

19. In a radiator, a tube having front and 1 rear faces and side walls,said side walls being corrugatedin substantially semi-circularcorrugations, said front and rear faces having folds of metal about theends of the corrugations, said front and rear faces lying atsubstantially right angles to the side walls.

20. In a radiator, a tube having front and rear faces and side walls,said side walls being corrugated insubstantially semi-circularcorrugations, -said out and rear corrugations, said front and rearfaceshav- .ing folds of metal about the ends of the cor- Vends Ofthe'cQIrRgatiOns; 1 ant? and wai 6 gamma faces be" thikened byshrihkage of tha22. The method of forming out of sheet metal aniafi1gg flds .of .meta1mm he .nmm} a wrmgnted wbe havmg sicie walls which om-prises laterally21\. I;[n the process desaribed, thasteps of displacing @sarts .0f themetal which form 1 I forming a .Sheet inbo; a'pair 0f gutters with theside we Is, and simultxz necusly crushing a folding margm'fiatween thetwo gutters together the adjacent parts of the metal 8h1:ink'ing 3 113;of the gathers, includmg the forming the and walls.

fo'lding margmto thi n the metal thereat In WAEIIBSS Whmufil heiemitosubscribe" smoothingout the metal along a folding lins y hams this 8thday. of October, A. D. 2

on. :said margin and folding,- said gutters o- 1918.

ward each'other on said line; I FRED M. OPITZ.

